Fluid permeable heater assembly for an aerosol-generating system and method for assembling a fluid permeable heater for an aerosol-generating system

ABSTRACT

A cartridge for an aerosol-generating system is provided, including a liquid storage portion including a housing containing a liquid aerosol-forming substrate, the housing having an open end; and a heater assembly including: an electrical heating element configured to heat the substrate to form an aerosol, the heating element including a planar filament arrangement having one or more electrically conductive filaments, an electrically insulating substrate having a planar attachment face, the filament arrangement disposed on the planar attachment face, and clamping elements mechanically fixing the filament arrangement to the electrically insulating substrate and applying a pulling force onto the filament arrangement, at least a portion of the heater assembly being fluid-permeable, and the heater assembly being arranged over the open end of the housing.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation application of and claims benefitunder 35 U.S.C. § 120 to U.S. application Ser. No. 17/402,146, filed onAug. 13, 2021, which is a continuation application of and claims benefitunder 35 U.S.C. § 120 to U.S. application Ser. No. 16/190,317, filed onNov. 14, 2018 (now U.S. Pat. No. 11,153,937), which is a continuationapplication of and claims benefit under 35 U.S.C. § 120 to U.S.application Ser. No. 15/110,987, filed on Jul. 12, 2016 (now U.S. Pat.No. 10,149,498), which is a U.S. National Stage application ofPCT/EP2014/077827, filed on Dec. 15, 2014, and claims benefit ofpriority under 35 U.S.C. § 119 to EP Application Nos. 14154554.1,14154553.3, and 14154552.5, each filed on Feb. 10, 2014, the entirecontents of each of which are incorporated herein by reference.

The invention relates to a fluid permeable heater assembly foraerosol-generating systems and a method for assembling a fluid permeableheater. Especially, the invention relates to a fluid permeable heaterassembly for handheld aerosol-generating systems, such as electricallyoperated smoking systems.

Some aerosol-generating systems such as electrically operated smokingdevices may comprise a battery and control electronics, a cartridgecomprising a supply of aerosol forming substrate and an electricallyoperated vaporizer. A substance is vaporized from the aerosol formingsubstrate, for example by a heating element. The heating element may bean at least partially fluid permeable heater, for example a flat coilembedded in a ceramic material. However, such heaters are expensive inmanufacture.

There is a need for a fluid permeable heater assembly foraerosol-generating systems, which is inexpensive to produce and issimple in manufacture. There is also need for an according method forassembling fluid permeable heaters.

According to a first aspect of the invention, there is provided a fluidpermeable heater assembly for aerosol-generating systems, preferablyelectrically operated smoking systems. The fluid permeable heaterassembly comprises a substrate, preferably an electrically insulatingsubstrate. The substrate comprises an opening extending through thesubstrate. The heater assembly further comprises an electricallyconductive substantially flat filament arrangement arranged over theopening in the substrate. The filament arrangement is mechanically fixedto the substrate with clamping means. The clamping means are alsoelectrically conductive and serve as electrical contacts for providing aheating current through the filament arrangement as well as forstabilizing the filament arrangement clamped to the substrate.

Preferably, the heater assembly is assembled by mechanical means only. Afixation of the filament arrangement and substrate to each other, aswell as electrical contact between filament arrangement and a contactfor an external power source, for example a battery, is done bymechanical clamping. The clamping means provide for a secure fixation ofthe filament arrangement and for a reliable contact between the filamentarrangement and the clamping means. Due to the mechanical clamping andestablishing of the electrical contacting of the filament arrangement bymechanical means, no soldering, welding or etching of electricalcontacts is required. This may facilitate manufacture and reduce costsof manufacturing parts of the heater assembly. Further this may alsofacilitate machinability of the heater assembly or of parts thereof. Inaddition, the mechanical fixation may improve reliability of the heaterassembly by avoiding common issues of soldering and welding such as coldsolder joints or cold welds. These are known for low strength, forfailure under stress and for unreliable resistance. In addition, thefilament arrangement does not come into direct contact with connectorsof a battery of an aerosol-generating system, thus avoiding tearing ofthe filament arrangement upon insertion of the heater into the system.

With the method for assembling such a fluid permeable heater accordingto the invention three purposes may be combined in one single economicmeans: fixation of the filament arrangement to the substrate,stabilizing the filament arrangement in a plane and providing anelectrical connector to a power source, for example an e-cigarettebattery. The clamping means, corresponding clamping mechanism of afilament arrangement to a substrate and a corresponding assemblingprocess is cost effective, industrially proof, functionally efficient,robust and compatible with a relatively small surface of a heaterassembly.

The term “substantially flat” filament arrangement is used throughoutthe specification to refer to a filament arrangement that is in the formof a substantially two dimensional topological manifold. Thus, thesubstantially flat filament arrangement extends in two dimensions alonga surface substantially more than in a third dimension. In particular,the dimensions of the substantially flat filament arrangement in the twodimensions within the surface is at least 5 times larger than in thethird dimension, normal to the surface. An example of a substantiallyflat filament arrangement is a structure between two substantiallyparallel imaginary surfaces, wherein the distance between these twoimaginary surfaces is substantially smaller than the extension withinthe surfaces. In some embodiments, the substantially flat filamentarrangement is planar. In other embodiments, the substantially flatfilament arrangement is curved along one or more dimensions, for exampleforming a dome shape or bridge shape.

The term “filament” is used throughout the specification to refer to anelectrical path arranged between two electrical contacts. A filament mayarbitrarily branch off and diverge into several paths or filaments,respectively, or may converge from several electrical paths into onepath. A filament may have a round, square, flat or any other form ofcross-section. A filament may be arranged in a straight or curvedmanner.

The term “filament arrangement” is used throughout the specification torefer to an arrangement of one or preferably a plurality of filaments.The filament arrangement may be an array of filaments, for examplearranged parallel to each other. Preferably, the filaments may form amesh. The mesh may be woven or non-woven. Preferably, the filamentarrangement has a thickness of between about 0.5 micrometers and 500micrometers.

As a general rule, whenever the term “about” is used in connection witha particular value throughout this application this is to be understoodsuch that the value following the term “about” does not have to beexactly the particular value due to technical considerations. However,the term “about” used in connection with a particular value is always tobe understood to include and also to explicitly disclose the particularvalue following the term “about”.

For example, the shape of a substrate and filament arrangement clampedto the substrate may be adapted to the shape of an end of a cartridgecontaining the aerosol-forming substance. Such an end of a cartridge maybe planar but may also be curved, for example have a convex shape.

The opening in the substrate may substantially have any shape.Preferably, the opening has a simple shape easy to manufacture such asfor example a circular, oval or rectangular shape, that is, a cylinderhaving a circular, oval or rectangular base extending through thesubstrate. Preferably, the opening in the substrate includes at least acentral portion of the substrate. The central portion includes thefictive center of gravity of the substrate. Alternatively, or inaddition, the central portion may comprise a longitudinal axis, forexample a rotational axis, like, for example, the rotational axis of acircular disc shaped substrate.

The substantially flat filament arrangement is arranged over at least aportion of the opening by the clamping means. The substrate comprises anattachment face, where the substantially flat filament arrangement ispositioned against in the mounted state. Preferably, the attachment faceis a portion of the top surface of the substrate. The attachment facemay include the opening as well as portions of the top surface of thesubstrate adjacent the opening. Preferably, the attachment face isplanar. The clamping means apply a pulling force onto the filamentarrangement. This pulling force is directed into at least a directioncoplanar to the attachment face. Preferably, the pulling force isapplied to the filament arrangement during assembly of the heater andpreferably in the mounted state of the filament arrangement. The pullingforce supports the planar arrangement of the filament arrangement andhelps to stabilize the filament arrangement in the plane of thesubstrate. Preferably, the clamping means provide opposite pullingforces to the filament arrangement, stretching and stabilizing thefilament arrangement in a plane.

The clamping means may comprise several separately arranged clampingelements, preferably two separately arranged clamping elements.Preferably, the separate clamping elements do not directly contact eachother such that the separate elements form two contacts for applyingpower to the heater and heating the filament arrangement. More than oneclamping element may serve as one electrical contact for the filamentarrangement. More than one clamping element may serve as secondelectrical contact for the filament arrangement. Preferably, theclamping means are two electrically conductive clamping elements,preferably having shapes of clamps, clips or staples. Preferably,clamping means provide a clamping action along a line, thus preventingfilament damage or tearing due to single point fixing. Preferably, thetwo clamping elements are arranged opposite each other, for example onopposite lateral sides of the substrate. Preferably, the heater assemblycomprises few components, like for example, only a substrate, a filamentarrangement and two clamping elements. A clamping means may alsocomprise a shape adapted to the form of an external connector forsimplifying a connection and improving an external electrical contact.

Fluid permeable heater assemblies are suitable for vaporizing liquids ofdifferent kind of cartridges. For example, as an aerosol-formingsubstrate, a cartridge may contain a liquid or a liquid containingtransport material such as for example a capillary material. Such atransport material and capillary material actively conveys liquid and ispreferably oriented in the cartridge to convey liquid to the heaterassembly. The filament arrangement is arranged close to the liquid or tothe liquid containing capillary material such that heat produced by thefilament arrangement may vaporize the liquid. Preferably, filamentarrangement and aerosol-forming substrate are arranged such that liquidmay flow into interstices of the filament arrangement by capillaryaction. The filament arrangement may also be in physical contact with acapillary material.

The electrically conductive filaments may define interstices between thefilaments and the interstices may have a width of between 10 micrometersand 100 micrometers. Preferably the filaments give rise to capillaryaction in the interstices, so that in use, liquid to be vaporised isdrawn into the interstices, increasing the contact area between theheater assembly and the liquid. The electrically conductive filamentsmay form a mesh of sizes between 160 Mesh US and 600 Mesh US (plus orminus 10 percent (that is between 160 and 600 filaments per inch (plusor minus 10 percent)). The width of the interstices is preferablybetween 75 micrometers and 25 micrometers.

The percentage of open area of a mesh, which is the ratio of the area ofthe interstices to the total area of the mesh is preferably between 25and 60 percent. The mesh may be formed using different types of weave orlattice structures.

The filament arrangement may also be characterised by its ability toretain liquid, as is well understood in the art.

The electrically conductive filaments may have a diameter of between 10micrometers and 100 micrometers, preferably between 8 micrometers and 50micrometers, and more preferably between 8 micrometers and 40micrometers. The area of the filament arrangement may be small,preferably less than or equal to 25 square millimeter, allowing it to beincorporated into a handheld system. The filament arrangement may, forexample, be rectangular and have dimensions of 5 millimeter by 2millimeter in the mounted state. Preferably, a filament arrangementcovers an area of between 10 percent and 50 percent of the area of theheater assembly. More preferably, the filament arrangement covers anarea of between 15 and 25 percent of the area of the heater assembly.

The filament arrangement may be formed by etching a sheet material, suchas a foil. This may be particularly advantageous when the heaterassembly comprises an array of parallel filaments. If the heaterassembly comprises a mesh, the filaments may be individually formed andknitted or waved together.

The filaments of the heater assembly may be formed from any materialwith suitable electrical properties. Suitable materials include but arenot limited to: semiconductors such as doped ceramics, electrically“conductive” ceramics (such as, for example, molybdenum disilicide),carbon, graphite, metals, metal alloys and composite materials made of aceramic material and a metallic material. Such composite materials maycomprise doped or undoped ceramics. Examples of suitable doped ceramicsinclude doped silicon carbides. Examples of suitable metals includetitanium, zirconium, tantalum and metals from the platinum group.Examples of suitable metal alloys include stainless steel, constantan,nickel-, cobalt-, chromium-, aluminium-, titanium-, zirconium-,hafnium-, niobium-, molybdenum-, tantalum-, tungsten-, tin-, gallium-,manganese- and iron-containing alloys, and super-alloys based on nickel,iron, cobalt, stainless steel, Timetal®, iron-aluminium based alloys andiron-manganese-aluminium based alloys. Timetal® is a registered trademark of Titanium Metals Corporation. The filaments may be coated withone or more insulators. Preferred materials for the electricallyconductive filaments are 304, 316, 304L, 315L stainless steel, andgraphite.

The electrical resistance of the filament arrangement is preferablybetween 0.3 Ohms and 4 Ohms. More preferably, the electrical resistanceof the filament arrangement is between 0.5 Ohms and 3 Ohms, and morepreferably about 1 Ohm. The electrical resistance of the filamentarrangement is preferably at least an order of magnitude, and morepreferably at least two orders of magnitude, greater than the electricalresistance of the contact portions. This ensures that the heat generatedby passing current through the heater assembly is localised to thefilament arrangement. It is advantageous to have a low overallresistance for the heater assembly if a system is powered by a battery.A low resistance, high current system allows for the delivery of highpower to the heater element. This allows the heater element to heat theelectrically conductive filament arrangement to a desired temperaturequickly.

The heater assembly may comprise at least one filament made from a firstmaterial and at least one filament made from a second material differentfrom the first material. This may be beneficial for electrical ormechanical reasons. For example, one or more of the filaments may beformed from a material having a resistance that varies significantlywith temperature, such as for example an iron aluminium alloy. Thisallows a measure of resistance of the filaments to be used to determinetemperature or changes in temperature. This can be used in a puffdetection system. Alternatively, or in addition, this can be used forcontrolling the heater temperature to keep it within a desiredtemperature range. Sudden changes in temperature may also be used as ameans to detect changes in air flow past the heater assembly resultingfrom a user puffing on an electrically operated smoking system. Apreferred embodiment of this kind of filament material is, for example,an array of parallel filaments of a first material arranged above anarray of parallel filaments of a second material, the arrays rotatedversus each other forming a mesh. A combination of materials may also beused to improve the control of the resistance of the substantially flatfilament arrangement. For example, materials with a high intrinsicresistance may be combined with materials with a low intrinsicresistance. This may be advantageous if one of the materials is morebeneficial from other perspectives, for example price, machinability orother physical and chemical parameters. For example, one of thematerials may be stainless steel.

Preferably, the substrate of the heater assembly is electricallyinsulating. The electrically insulating substrate may comprise anysuitable material, and is preferably a material that is able to toleratehigh temperatures (in excess of 300 degree Celsius) and rapidtemperature changes. An example of a suitable material is a polyimidefilm, such as Kapton®, Polyetheretherketone (PEEK) or a ceramicsmaterial, preferably an open pored electrically insulating ceramicmaterial. Preferably, the material of the substrate is non-brittle. Thesubstrate material may have capillary action for liquid to be vaporized.

Preferably, the substrate is substantially flat. Preferably, thesubstrate is a disc, wherein the disc may be, for example, circular,oval or rectangular. The disc may be planar or curved. Preferably, thesubstrate also comprises a planar attachment face to be arranged facinga cartridge containing the aerosol-forming substrate such that theheater assembly and the cartridge, or a cover of the cartridge,respectively, have a planar contact surface. This allows for a flusharrangement of cartridge and heater assembly.

According to an aspect of the fluid permeable heater assembly accordingto the invention, the clamping means mechanically fixing the filamentarrangement to the substrate provide a form-fit closure or a force-fitclosure with the substrate. Form-fit and force-fit closures are twotypes of mechanical fixing, which are simple and secure for mechanicallyfixing components to each other. The two types of closure may becombined. In a form-fit closure, the clamping means and the substratecomprise corresponding forms. A fixation may be mainly or solely due tofrictional forces between the interface of clamping means and substratein a contact area. However, a form-fit closure may also be achieved, forexample, by an enveloping of filament and substrate by the clampingmeans. In a force-fit closure, clamping means or substrate or both,clamping means and substrate, may comprise resilient portions, forexample flexible legs or spring-like elements. The force applied by theclamping means or parts of the clamping means keep the filamentarrangement affixed to the substrate.

Force-fit and form-fit closure may also be combined in a clampingmechanism of clamping means and substrate. For example a clamping meansmay contain parts made of a resilient material. Alternatively, or inaddition, the clamping means may comprise a form that deviates from theform of a corresponding portion in the substrate. For example, aconically formed leg of a clamping means may be inserted into a recessin the substrate, wherein the recess has parallel inner walls.

According to another aspect of the fluid permeable heater assemblyaccording to the invention, the clamping means extend over a portion ofa lateral side of the substrate and comprise resilient leg portions. Theresilient leg portions press the filament arrangement to a top surfaceof the substrate. Therein, filament arrangement and substrate arearranged in between the resilient legs. The filament arrangement andsubstrate are clamped in between the resilient leg portions, for exampleleaf springs, of the clamping means. The spring force of the resilientleg portions defines the clamping force. The portion of the clampingmeans extending over the lateral side of the substrate may serve aselectrical contact to an external power source. By this an electricalcontacting of the heater assembly may occur from a top or bottom of theheater assembly but also or only from a lateral side. This may simplifycontacting of the heater assembly with electrical connectors beingarranged along inner walls of a main housing of an aerosol generatingsystem. A contacting may also be improved due to connectors beingcontactable to more than one side of the heater assembly.

According to a further aspect of the fluid permeable heater assemblyaccording to the invention, the substrate comprises recesses forreceiving the filament arrangement and the clamping means in therecesses. Recesses may improve a clamping and contacting of the filamentarrangement, due to a localization of the contacting location of theclamping means on or in the substrate. Recesses may also aid in defininga contacting area, for example a position or size of a contact area. Arecess may for example also limit or prohibit a displacement, forexample sliding, of the clamping means from the substrate or on thefilament arrangement during assembly or in the assembled state. Recessesmay be provided in a surface of the substrate, preferably a top surfaceand a bottom surface of the substrate. Recesses may extend partly intoor may extend entirely through the substrate. Recesses may for examplebe grooves, holes or slits.

According to an aspect of the fluid permeable heater assembly accordingto the invention, the clamping means are staple-like elements insertedinto recesses of the substrate. A staple-like element is basicallyu-shaped having two legs and a bridge portion between the legs.Staple-like element are simple in manufacture at low cost. Staple-likeelements may easily be assembled with a substrate, for example by alinear pushing action. Thereby, the legs of the staple-like elements maybe inserted into holes or recesses in the substrate, while the filamentarrangement is arranged between substrate and staple-like element.During assembly, the filament arrangement is not at risk to be displacedbut clamped upon contact of clamping means and substrate. Staple-likeelements allow for different clamping mechanisms or variations thereof.For example, for a form-fit closure the legs may be inserted into holesin the substrate, protruding ends of the legs may be bent on the bottomsurface of substrate and provide additional fixation of the clampingmeans on the substrate. Also a fixation of the filament arrangement, aswell as a surface for the electrical contact between filament andclamping means may be improved by simple means when using staple-likeelements. In some preferred embodiments this is done by recesses andstaple-like elements comprising corresponding but non-planar contactsurfaces. Therein ‘non-planar contact surfaces’ is understood to alsoinclude contact surfaces, which consist of several partial contactsurfaces, which partial surfaces may be flat but which are arranged atan angle to each other, such that the contact surface is non-planar.

An enlarged contact surface secures good electrical contact betweenfilament and clamping means. Due to an additional structure in thecontact surface, also a fixation of the filament arrangement may beimproved. A pulling force onto the filament arrangement may be enhanced,improving the stability of the filament arrangement. A side of thestaple-like element facing a recess in the substrate may have anon-planar form. This non-planar form may also be present on the side ofthe staple-like element to be contacted by a connector of a battery.Thus, also a contact area between clamping means and external connectormay be enlarged and improved.

According to another aspect of the fluid permeable heater assemblyaccording to the invention, the recesses are one or a combination oflongitudinal recesses extending across at least a portion of a topsurface of the substrate, individual through bores within the substrateor recesses in a circumference of the substrate. The different kind ofrecesses allow for a wide variety of clamping mechanisms and differentembodiments and shapes of substrates and clamping means. Preferably,longitudinal recesses provided in the top surface of the substrateprovide large contact areas. Longitudinal recesses may extend across apart or across the entire top surface of the substrate. Also a bottomsurface may be provided with longitudinal recesses. Longitudinalrecesses allow for flat heater assembly constructions due to acountersinking available for the clamping means in the recesses.Longitudinal recesses in a top surface of the substrate are especiallypreferred for clamping means that extend over a lateral side of thesubstrate and for clamping means having resilient leg portions that areentirely inserted into recess. In the latter embodiments, a clampingforce acts inside the substrate. A longitudinal recess may also improvea clamping, where longitudinal edges of clamping means press against thetop surface and the bottom surface of the substrate.

Bore holes or recesses in a circumference of a substrate allow a formfit closure of clamping means and substrate by providing a clampingmeans on the top surface and the bottom surface, however without addingmaterial to a lateral side of the heater assembly. Thus, dimensionalrestrictions, for example of a main housing of a system will not bechallenged by the heater assembly.

In some preferred embodiments of the fluid permeable heater assembly,the clamping means comprise resilient leg portions, which are arrangedand clamped within the longitudinal recesses. In these embodiments, aclamping force acts in a lateral direction of the substrate and insidethe substrate. The clamping means, especially the clamping action of theresilient leg portions arranged inside the recesses are well protectedfrom influences of external elements, for example system elementsarranged on top or below the heater assembly. Thus, a loosening effectof the clamping action, for example by a housing wall pressing againstthe clamping means may be avoided. Preferably, the clamping means arecountersunk in the substrate, even more preferably substantiallycompletely countersunk in the substrate except for a flat contact area.This facilitates the handling of the substrate during the manufacture ofa very compact heater assembly.

A filament arrangement may extend partially or entirely over the openingin the substrate. Preferably, the filament arrangement covers about 50percent to about 95 percent of the opening, for example covers betweenabout 70 percent to about 90 percent of the opening in the substrate.

If the filament arrangement covers the entire opening, a maximalavailable area of a liquid surface or of an aerosol forming substratearranged next to the heater is heated. Thus, high vaporization isachievable since heat is applied to a large surface. In addition,depending on the kind of aerosol forming substrate, for example acapillary material transporting liquid to the heater, a large heatedarea may support a homogeneous draining of the aerosol-formingsubstrate. At the same time, the area not covered by the substantiallyflat filament arrangement may contribute differently to the aerosolgeneration in terms of flow rate or droplet size. This may be beneficialin order to optimize the generation of an aerosol with predeterminedcharacteristics in a repeatable manner. For example, if the filamentarrangement does not cover the entire opening, vaporized liquid may moreeasily pass through the heater assembly in those regions not covered bythe filament arrangement. By this, aerosol production may be supported.

Preferably, the substantially flat filament arrangement is in directcontact with the capillary material transporting liquid to the heater.This facilitates a continuous stream of liquid to the substantially flatfilament arrangement for the generation of an aerosol. Preferably, thetransport medium is homogeneous.

In some preferred embodiments of the fluid permeable heater assemblyaccording to the invention, the filament arrangement comprises aplurality of filaments forming a mesh.

A mesh provides a stable and robust filament arrangement. It alsoprovides an easy handling during manufacture, easier than for example anarray of filaments arranged parallel to each other. In addition, anability of the mesh to retain liquid between the filaments may beselected and varied, for example, by varying a type of weaving or alattice structure. A mesh is robust in a structural sense: Thus, a meshhas excellent fail-safe properties due to the redundancy of availableelectrical paths. Even if one filament of the mesh is broken orincompletely contacted the heater may still be operated with littlechange of overall electrical a thermal performance of the filamentarrangement.

In some preferred embodiments of the fluid permeable heater assemblyaccording to the invention, the substrate is an electrically isolating,substantially flat, preferably disc-shaped element. A flat heaterassembly is space saving and provides easy handling upon manufacture andassembly of a system.

According to another aspect of the invention, there is provided a methodfor assembling a mesh heater for an aerosol-generating system. Themethod comprises the steps of providing a substrate, providing anopening through the substrate and arranging electrically conductivefilaments over the opening of the substrate. Further steps of the methodare mechanically fixing the filaments to the substrate by clampingmeans, thus clamping the filaments to the substrate, and providing anelectrical contact to the filaments through the clamping means.

According to an aspect of the method according to the invention, themethod further comprises the step of providing recesses in the substrateand pushing the clamping means into the recesses. By such a pushing,clamping means may be applied to the prepared filament-substrateconfiguration by a linear movement. This enables to assemble a heater inone single clamping step. A pushing may be performed substantiallyperpendicular to the substrate or substantially parallel to thesubstrate. A pushing substantially perpendicular to the substraterelates to a pushing from above the substrate against the top surface. Asubstantially parallel pushing relates to sideway application of theclamping means from a lateral side of the substrate or to an applicationof the clamping means by sliding the clamping means on thefilament-substrate configuration.

Preferably, the step of insertion of the clamping means creates astretching force in the direction of the plane of the substantially flatfilament arrangement. This advantageously stretches the substantiallyflat filament arrangement to a predetermined tension. This allows for animproved contact surface between the substantially flat filamentarrangement and the substrate. Further, this allows for an improvedcontact surface between the substantially flat filament arrangement andthe transport medium.

According to another aspect of the method according to the invention, aclamping force acts in a direction substantially perpendicular to a topsurface of the substrate. Typical representatives of such embodimentsare for example sandwich clamping means, where the filament arrangementand substrate is sandwiched between portions of the clamping means.

According to another aspect of the method according to the invention, aclamping force acts in a direction substantially lateral to a topsurface and within the substrate. Representatives of such embodimentsare for example clamping means, which are arranged within the substrate,preferably within a recess in the substrate provided for receiving theclamping means or that part of the clamping means provided for clamping.Another part of the clamping means provided for an electrical contactingof the clamping means is then arranged outside of the recess.

According to another aspect of the method according to the invention,the filament arrangement includes a first portion and second portionsthat form an integrated filament, wherein the second portions areprovided on either end of the filament arrangement and the first portionis provided between the second portions. As used herein, “integrated”means that the first portion and the second portions form a single bodythat provides an electrical pathway from one second portion to the othersecond portion via the first portion.

In such a configuration, the second portions may be formed of adifferent material than the first portion or additionally oralternatively of the same material but provided in a different form. Forexample, where the filament arrangement comprises a mesh, the secondportions may take the different form of having a higher density meshthan in the first portion. Alternatively, the filament arrangement maybe formed of a two different materials in the first portion and thesecond portions, where the material forming the second portions is moremalleable and more easily deformed than the material of the firstportion. In this case, for example, the first portion may be formed ofstainless steel and the second portion may be formed of copper.Alternatively, the second portions may be formed of a foil between whichthe first portion is provided such that the first portion and secondportions form an integrated filament.

When the filament arrangement comprises first and second portions, thefilament arrangement may be subjected to an additional step where thesecond portions are subjected to sufficient force such that they form afoil-like material. As used herein, a “foil-like” material is anymaterial that is subject to a force that flattens the material whilemaintaining the integrated filament.

Further aspects and advantages of the method according to the inventionare mentioned relating to the fluid permeable heater assembly and willnot be repeated.

According to yet another aspect of the invention there is provided anaerosol generating system, preferably an electrically operated smokingsystem. The aerosol generating system comprises a storage portioncomprising a housing for holding a liquid aerosol-forming substrate,wherein the housing has an open end. The system further comprises afluid permeable heater assembly according to the invention and asdescribed herein. The heater assembly is arranged next to the housingsuch that the filament arrangement of the fluid permeable heaterassembly is arranged over the open end of the housing. The systemfurther comprises a connector of a power source for electricallyconnecting the clamping means of the fluid permeable heater assembly tothe power source.

Advantages and aspects of the aerosol generating system have beendescribed relating to the heater assembly and will not be repeated. Dueto the available variants of clamping means and according embodiments ofheater assembly, a heater assembly may be adapted and manufactured, forexample, to be suitable for existing main housings of such system. Suchmain housings may already include a cartridge containing anaerosol-forming substrate, electrical circuit, power source andelectrical connectors for contacting the heater assembly.

A storage portion advantageously contains a capillary material. Thecapillary material may have a fibrous or spongy structure. The capillarymaterial preferably comprises a bundle of capillaries. For example, thecapillary material may comprise a plurality of fibres or threads orother fine bore tubes. The fibres or threads may be generally aligned toconvey liquid to the heater. Alternatively, the capillary material maycomprise sponge-like or foam-like material. The structure of thecapillary material forms a plurality of small bores or tubes, throughwhich the liquid can be transported by capillary action. The capillarymaterial may comprise any suitable material or combination of materials.Examples of suitable materials are a sponge or foam material, ceramic-or graphite-based materials in the form of fibres or sintered powders,foamed metal or plastics material, a fibrous material, for example madeof spun or extruded fibres, such as cellulose acetate, polyester, orbonded polyolefin, polyethylene, terylene or polypropylene fibres, nylonfibres or ceramic, The capillary material may have any suitablecapillarity and porosity so as to be used with different liquid physicalproperties. The liquid has physical properties, including but notlimited to viscosity, surface tension, density, thermal conductivity,boiling point and vapour pressure, which allow the liquid to betransported through the capillary device by capillary action.

Preferably, the capillary material is in contact with the electricallyconductive filaments. The capillary material may extend into intersticesbetween the filaments. The heater assembly may draw liquidaerosol-forming substrate into the interstices by capillary action. Thecapillary material may be in contact with the electrically conductivefilaments over substantially the entire extent of the opening. Thecartridge may contain two or more different capillary materials, whereina first capillary material, in contact with the heater element, has ahigher thermal decomposition temperature and a second capillarymaterial, in contact with the first capillary material but not incontact with the heater element has a lower thermal decompositiontemperature. The first capillary material effectively acts as a spacerseparating the heater element from the second capillary material so thatthe second capillary material is not exposed to temperatures above itsthermal decomposition temperature. As used herein, “thermaldecomposition temperature” means the temperature at which a materialbegins to decompose and lose mass by generation of gaseous by products.The second capillary material may advantageously occupy a greater volumethan the first capillary material and may hold more aerosol-formingsubstrate that the first capillary material. The second capillarymaterial may have superior wicking performance to the first capillarymaterial. The second capillary material may be cheaper than the firstcapillary material. The second capillary material may be polypropylene.

The first capillary material may separate the heater assembly from thesecond capillary material by a distance of at least 1.5 millimeter, andpreferably between 1.5 millimeter and 2 millimeter in order to provide asufficient temperature drop across the first capillary material.

The storage portion may be positioned on a first side of theelectrically conductive filaments and an airflow channel positioned onan opposite side of the electrically conductive filaments to the liquidstorage portion, such that air flow past the electrically conductivefilaments entrains vaporised liquid aerosol-forming substrate.

The system may further comprise electric circuitry connected to theheater assembly and to an electrical power source, the electriccircuitry configured to monitor the electrical resistance of the heaterassembly or of one or more filaments of the heater assembly, and tocontrol the supply of power to the heater assembly dependent on theelectrical resistance of the heater assembly or the one or morefilaments.

The electric circuitry may comprise a microprocessor, which may be aprogrammable microprocessor. The electric circuitry may comprise furtherelectronic components. The electric circuitry may be configured toregulate a supply of power to the heater assembly. Power may be suppliedto the heater assembly continuously following activation of the systemor may be supplied intermittently, such as on a puff-by-puff basis.

The power may be supplied to the heater assembly in the form of pulsesof electrical current.

The system advantageously comprises a power supply, typically a battery,within the main body of the housing. As an alternative, the power supplymay be another form of charge storage device such as a capacitor. Thepower supply may have sufficient capacity to allow for the continuousgeneration of aerosol for a period of around six minutes. In anotherexample, the power supply may have sufficient capacity to allow for apredetermined number or discrete activations of the heater assembly.

The invention is further described with regard to embodiments, which areillustrated by means of the following drawings, wherein:

FIG. 1 shows an embodiment of a heater assembly;

FIG. 2 shows the heater assembly of FIG. 1 in a mounted state;

FIGS. 3 a and 3 b show details of clamping mechanisms;

FIGS. 4 a-4 d show further clamping means and clamping mechanisms;

FIGS. 5 a and 5 b show top views of the heater assembly;

FIGS. 6 a-6 c show a heater assembly with sideways slidable clampingmeans (FIG. 6 a ); details of the clamping mechanism (FIG. 6 b ); andclamping means (FIG. 6 c );

FIGS. 7 a and 7 b show a heater assembly with staples as clamping meansand details of parts of the cross section of the substrate;

FIG. 8 shows a further embodiment of a heater assembly with staples asclamping means;

FIG. 9 shows heater assemblies with mounted staples;

FIG. 10 shows a further embodiment of heater assembly with staples asclamping means;

FIGS. 11 a-11 d show filament arrangements having first and secondportions and methods for manufacturing integrated filaments; and

FIG. 12 shows an exploded view of an embodiment of an aerosol generatingsystem including a storage portion and a fluid-permeable heaterassembly.

In the figures, the same reference numerals are used for the same orsimilar elements.

In FIG. 1 and FIG. 2 a heater assembly including an electricallyinsulating substrate 1, a heater element and filament arrangement in theform of a mesh 2 and two clamps 3 for attaching the mesh to thesubstrate are shown. The substrate 1 has the form of a circular disc andcomprises a centrally arranged opening 100. The substrate also comprisestwo slits 4 arranged parallel to each other and next to each side of thesquare-formed opening 100. The mesh 2 in the form of a band is arrangedover the opening and over the slits 4. The width of the mesh is smallerthan the width of the opening 100 such that on both lateral sides of themesh an open portion 101 of the opening is formed, which open portionsare not covered by the mesh. The two clamps 3 comprise a flat contactportion 31 to be arranged parallel to the top surface of the substrate.The contact portions 31 are for contacting the heating assembly by anelectrical connector from a battery. The two clamps 3 also comprise alongitudinal folded clamping portion 30 for being inserted into theslits 4 in the substrate 1.

The clamps 3 may be folded from a piece of metal such as, for example, astainless steel or copper sheet.

FIG. 2 shows the heater assembly in an assembled state, wherein the mesh2 has been pushed into the slits 4 upon pushing the clamps 3perpendicular to the top surface into the slits (pushing direction isindicated by arrows in FIG. 1 ). By the clamps 3 a pulling force 5acting in a direction coplanar to the top surface of the substrate 1acts on the mesh 2. Each of the clamps 3 causes a pulling force 5 actingin opposite direction. This pulling force 5 supports the planararrangement of the mesh 2 and helps to stabilize the mesh in the planeof the substrate 1.

FIG. 3 a shows the detailed view of the inserted clamp 3 in slit 4. Endportions 20 of the mesh 2 are pushed into the slits by the clampingportions 30 of the clamps and securely clamped in the slits. The foldedclamp portions 30 execute a clamping force 50 onto the walls of theslits in a direction parallel to the top surface of the substrate andwithin the substrate. Edges 301 of the clamps 3 may act as barbs,additionally fixing the mesh in the slits and improve secure electricalcontact of clamps 3 with mesh 2.

FIG. 3 b shows an alternative embodiment of a folded clamping portion 30of a clamp 3 inserted in a longitudinal slit 4. The slit has convexwalls 6, which press the clamp at its narrowest folded part 7 of theinserted clamping portion 30. In this embodiment, the narrowest foldedpart 7 is in about half the height of the substrate 1. By this, the(larger) folded part 8 inserted deepest into the slit 4 is furtherprevented to leave the slit.

FIGS. 4 a to 4 d show embodiments of clamps 3, which clamp the substrate1 on the top surface and on the bottom surface. Upper and lower clampingedges 9, 10 press into the top and bottom surface of the substrate 1.The mesh 2 is arranged between at least the upper clamping edge 9 andthe top surface of the substrate. This upper edge 9 directs slightlyinto a backwards direction such as to have a more stable constructionwhen pulling the mesh 2 against this backward direction.

The clamps 3 comprise a lateral portion 32 arranged at a lateral orcircumferential side of the substrate 1. The lateral portion 32 of theclamps may further support a clamping and contacting of the mesh 2 bycontacting the lateral side of the substrate 1.

In FIGS. 4 a and 4 b the mesh 2 is guided around the circumference ofthe substrate 1 and is fixed to both sides of the substrate. Theclamping edges 9, 10 of the clamp 3 in FIG. 4 b do not extend along theentire longitudinal extension of the clamp. The edges are formed by cutouts of the clamp sheet bent to direct versus top or bottom surface,respectively, of the substrate 1.

Side walls of the clamp 3 in FIG. 4 c are smoothly bent altering theresiliency of the clamp. The top and bottom surface of the substrate 1is provided with longitudinal recesses 12, 13 in the form of notches forreceiving the clamp edges 9, 10, as well as the mesh 2 (upper recess 9only in this embodiment).

The lateral side 32 of the clamp 3 of FIG. 4 d closely contacts thelateral side of the substrate as well as a part of the bottom surface ofthe substrate 1. On the bottom surface, the clamp forms a triangle 33when seen from the side. The length of the triangle 33 may be adaptedand varied to vary a clamping force of the clamp 3.

A heater assembly provided with clamps as shown in FIGS. 4 a to 4 d maybe assembled by arranging the mesh 2 over the substrate 1 and by bendingthe clamps while assembling the heater. A pulling force on the mesh isthen provided upon bending the clamps.

FIGS. 5 a and 5 b show top views of heater assemblies with clamps havinglongitudinal clamping portions, such as for example shown in theembodiments of FIGS. 4 a to 4 d and FIGS. 6 a to 6 c . The clamps 3 inFIG. 5 a have a substantially rectangular form when seen from above orfrom below. Such clamps are simple to manufacture, for example bybending a rectangular piece of sheet material or wire. The clamps asshown in FIG. 5 b have forms adapted to the form of a substrate. Thus, acircular substrate is provided with clamps adopting the circular form ofthe circumference of the substrate. Such a heater assembly is verycompact and space saving also in lateral dimensions.

In FIGS. 6 a to 6 c a heater assembly and clips are shown, which clipsmay be slid onto the prepared substrate 1 and mesh 2 configuration. Thesubstrate has longitudinal recesses 12, 13 in the form of notches in thetop surface and in the bottom surface. The recesses 12, 13 are arrangedparallel to each other, parallel to the opening 100 in the surface andextend across the entire surface of the substrate 1. The recesses 12, 13facilitate the sideway sliding of the clips 3 onto the mesh-substrateconfiguration. Preferably, the mesh 2 is firmly stretched before slidingthe clips 3 onto the substrate 1. To prevent the tearing of the mesh ora getting caught in the mesh upon sliding on, the edges 15 of the clipare rounded. This may be seen in FIG. 6 c showing a pre-manufacturedclip 3 as clamping means.

In FIGS. 7 a, 7 b , 8, and 10 clamping means 3 in the form of twostaples and corresponding recesses 12 in the substrate 1 are shown. Amesh (not shown) is arranged over at least a portion of the opening 100in the substrate. The staples are vertically inserted into recesses 12,120, 122 in the substrate. In the mounted position, the bridges of thestaples come to lie in the longitudinal recesses 12 provided in the topsurface of the substrate 1. The legs have a length longer than thethickness of the substrate 1. The projecting leg ends are bent andcountersunk in corresponding recesses 19 in the bottom surface of thesubstrate. With the legs bent around the substrate, the mesh 2 issecurely clamped and contacted by the staple. In FIGS. 7 a and 8, thefour legs of the two staples are inserted into four recesses 121arranged in the circumference of the disc-formed substrate. In FIG. 7 a, the bridges of the staples have an embossed shape 17 in the form of aroof. Such a form may directly correspond to the form of connectors of abattery. The longitudinal recesses 12 in the substrate also have acorresponding roof-shaped form of the bottom of the recess 18 as may beseen in the cross sectional detailed view depicted in FIG. 7 b.

In FIG. 8 the bridges of the staples have an engraved v-shaped form 20,which corresponds to a corresponding engraved v-shape form 21 of therecesses 12.

A stretching of the mesh is caused by the corresponding shapes 17, 18;20, 21 of staple and recess 12.

FIG. 9 shows the two heating assemblies of FIG. 7 a and FIG. 8 in theassemble state. Therein, the heating assembly as shown in FIG. 7 acorresponds to the embodiment as shown on the bottom of FIG. 9 and FIG.8 corresponds to the embodiment shown on top of FIG. 9 .

FIG. 10 is a further variant of a heating assembly with staples asclamping means 3. The substrate is provided with two longitudinalrecesses 12 for receiving the bridge portion of the staples. Thesubstrate is also provided with one hole 122 at each end of thelongitudinal recesses 12. The legs of the staples are pushed into theholes 122 and a mesh (not shown) is clamped and contacted between therecess 12 and the staple. The staples 3 may be attached to the substrate1 by a form-fit between the legs of the staples and the holes 122.However, the bottom surface of the substrate may also be provided withrecesses for receiving leg ends bent at the bottom of the substrate.

FIGS. 11 a to 11 d illustrate methods of providing an integratedfilament having first and second portions. In FIG. 11 a , the firstportion is illustrated as a mesh 1101 and the second portions areillustrated as a higher density mesh 1103. For example, the firstportion may comprise a lower density mesh than the second portions butboth the first and second portions are formed of a single material, suchas stainless steel. In FIG. 1 ib, the first portion is illustrated as amesh 1101 comprising a first material and the second portions 1105 areillustrated as end portions being formed of a second material other thanthe first material. Therein, the second material is more malleable thanthe first material. As an example, first portion 1101 may be stainlesssteel and the second portion 1105 may be copper. FIG. 11 c illustratessubjecting the second portions 1108 to a force with pressing elements1107 such that the second portions 1108 are deformed and are a foil-likematerial 1109 as illustrated in FIG. 11 d.

After forming the resulting integrated filament including first 1101 andsecond portions 1103, 1105, 1109, the integrated filament may be affixedto a substrate using one of the methods described above by providing thesecond portions 1103, 1105, 1109 such that clamps 3 are electricallyconnected to the second portions.

In FIG. 12 , an exploded view of an aerosol generating system 1200,preferably an electrically operated smoking system, is shown. Theaerosol generating system 1200 comprises a liquid storage portion 1210comprising a housing for holding a liquid aerosol-forming substrate1215, wherein the housing has an open end 1220. The aerosol generatingsystem 1200 further comprises a fluid-permeable heater assembly 1225according to the invention and as described herein. The fluid-permeableheater assembly 1225 is arranged next to the housing such that theelectrical heating element (filament arrangement 1230) of thefluid-permeable heater assembly 1225 is arranged over the open end ofthe housing. The aerosol generating system 1200 further comprises anelectrically insulating substrate 1235 having a planar attachment faceon which the filament arrangement 1230 is disposed in contact, andconnectors (electrical contacts 1240) of a power source for applyingelectrical power to the filament arrangement 1230 of the fluid-permeableheater assembly 1225.

The invention has been described in more detail by means of theembodiments shown in the drawings. However, further embodiments ofclamping mechanisms and corresponding clamping means and substrate formsmay be envisaged. For example, a mesh may be attached to the substrateby screws. The screws then are electrically conductive and serve aselectrical contacts for the filament arrangement and as connectors for abattery. There may also be a clipping engagement between the clampingmeans and the substrate in the form of, for example, a press button orsnap fastener. Therein, a clamping means forms one part of the snapfastener and the substrate is provided with the corresponding other partof the snap fastener.

1. A cartridge for an aerosol-generating system, the cartridgecomprising: a liquid storage portion comprising a housing containing aliquid aerosol-forming substrate, the housing having an open end; and aheater assembly comprising: an electrical heating element configured toheat the liquid aerosol-forming substrate to form an aerosol, theelectrical heating element including a planar filament arrangementhaving one or more electrically conductive filaments, an electricallyinsulating substrate having a planar attachment face, the filamentarrangement being disposed on the planar attachment face, and clampingelements mechanically fixing the filament arrangement to theelectrically insulating substrate and applying a pulling force onto thefilament arrangement, wherein at least a portion of the heater assemblyis fluid-permeable, and wherein the heater assembly is arranged over theopen end of the housing.
 2. The cartridge according to claim 1, whereinthe clamping elements are configured to apply a pulling force into adirection coplanar to the planar attachment face.
 3. The cartridgeaccording to claim 1, where the clamping elements are configured toapply opposite pulling forces.
 4. The cartridge according to claim 1,wherein the clamping elements are electrically conductive and serve aselectrical contacts configured to provide an electrical current throughthe filament arrangement.
 5. The cartridge according to claim 1, whereinthe one or more electrically conductive filaments has a flatcross-section.
 6. The cartridge according to claim 1, wherein theelectrically insulating substrate further comprises an open-poredceramic material.
 7. The cartridge according to claim 1, furthercomprising a capillary material, wherein the filament arrangement isdisposed in physical contact with the capillary material.
 8. Thecartridge according to claim 1, wherein the filament arrangementcomprises a woven mesh.
 9. The cartridge according to claim 1, whereinthe electrically insulating substrate has an opening.
 10. The cartridgeaccording to claim 9, wherein the planar attachment face includes theopening.
 11. The cartridge according to claim 9, wherein the opening ofthe electrically insulating substrate extends through the electricallyinsulating substrate.
 12. The cartridge according to claim 9, whereinthe filament arrangement extends at least partially over the opening ofthe electrically insulating substrate.
 13. The cartridge according toclaim 1, wherein the electrically insulating substrate has holes formedtherein, and wherein the clamping elements extend into the holes. 14.The cartridge according to claim 1, wherein the electrically insulatingsubstrate has recesses formed therein, and wherein the clamping elementsextend into the recesses.
 15. The cartridge according to claim 1,wherein the electrically insulating substrate has holes formed therein,and wherein the holes extend partly through the electrically insulatingsubstrate.
 16. The cartridge according to claim 1, wherein the filamentarrangement has a first portion and second portions, the second portionsprovided on either end of the first portion of the filament arrangement,the first portion and the second portions being an integrated electricalpathway.
 17. The cartridge according to claim 1, wherein the filamentarrangement has a first portion and second portions, the second portionsprovided on either end of the first portion of the filament arrangement,the first portion and the second portions are formed of a singlematerial, wherein the first portion of the filament arrangementcomprises a mesh having a first density, wherein the second portions ofthe filament arrangement comprise the mesh having a second density, andwherein the second density is greater than the first density.
 18. Thecartridge according to claim 17, wherein the mesh is a woven mesh. 19.The cartridge according to claim 1, wherein the electrically insulatingsubstrate has two planar attachment faces.
 20. The cartridge accordingto claim 1, wherein the liquid aerosol-forming substrate is disposed ona first side of the planar filament arrangement and an airflow channelis disposed on an opposite side of the planar filament arrangement.